The objective of the proposed research is to obtain data, both in vivo and in vitro essential to understanding the transitions in metabolism during differentiation, aging and death in Dictyostelium discoideum. Specific projects include: l. Pertubation Studies: Short-term pertubation experiments will be continued, in which young sorocarps are exposed for 90 min to metabolites singly and in combination (glucose, Pi, uracil, nucleotides, pentose, and nucleoside monophosphates). Thereafter, the levels of trehalose, glycogen, cellulose, glucose-6-P, UDP-glucose and ATP will be measured. 2. The Citric Acid Cycle: A steady-state model is being constructed. Pulse-labelling of the TCA cycle intermediates has been carried out with preculminating cells using (14C)-glutamate, and will next be done with (l4C)--aspartate and (l4C)-alanine. The data will be interpreted with the aid of a computer program for constructing a steady-state model. 3. The localization and Significance of Trehalose and Glycogen in Sorocarps: Ultrastructural studies will be carried out on normal spores and on spores containing 5 - 6- fold higher levels of trehalose and glycogen. Comparative studies will also be done to determine possible differences in spore viability during aging under conditions of environmental stress. 4. Cellulose Synthesis: Various procedures will be employed to obtain cell-free pellet enzyme preparations for the incorporation of radioactive precursors into glucolipids, water soluble glucoproteins, and cellulose. Utilizing these preparations and our in vitro system for studying cellulose synthesis in Dictyostelium, investigations into the mechanisms of cellulose synthesis will be continued.